Apparatus for testing the operation of the defrost switch in an air conditioning unit

ABSTRACT

The present invention is an improvement in air conditioning system and comprises apparatus for testing the defrost switch in the air conditioning system. The apparatus comprises a pressure reservoir, means for filling the reservoir with fluid pressure, a pressure gauge, conduit means connecting the reservoir with the pressure gauge and with the defrost switch, and means such as a light or horn indicating successful operation of the defrost switch. Successful operation of the switch is clearly indicated by the light or horn even in noisy environments, and the pressure at which the switch operates can be read on the pressure gauge.

Unlted States Patent 1 91 [111 3,831,391

Blomstrand Aug. 27, 1974 [54] APPARATUS FOR TESTING THE 2,968,275 l/1961Spiro 62/128 OPERATION OF THE DEFROST SWITCH IN 3,106,833 10/ 1963Russell 324/28 R X 3,359,749 12/1969 Howland et al.. 62/140 AN AIRCONDITIONING UNIT 3,486,241 12/1969 Coyle 6161 34/54 x [75] Inventor:Paul R. Blomstrand, St. Louis Y, Primary ExaminerWilliam F. ODeaAssistant Examiner-Peter D. Fer son 73 A ACF 1 sslgnee lgg f ncorporatedNew Attorney, Agent, or FirmHenry W. Cummings 1 pp 319,820 The presentinvention is an improvement in air conditioning system and comprisesapparatus for testing the 52 us. c1 62/125, 62/126, 73/4 R, defrostSwitch in the ah conditioning System The 1 324/28 R paratus comprises apressure reservoir, means for fill- 51 1m. (:1 F25b 49/00 ing thereservoir with fluid Pressure, a Pressure gauge, [58] Field of Search62/126, 127 128, 131 conduit means connecting the reservoir with thepres- 62/140 124; 73/4 R; 324/28 R sure gauge and with the defrostswitch, and means such as a light or horn indicating successfuloperation [56] References Cited of the defrost switch. Successfuloperation of the UNTED STATES PATENTS switch is clearly indicated by thelight or horn even in noisy environments, and the pressure at which the73/4 R Switch Operates Canbe read o the pressure gauge e 2.490.82112/1949 Leonard 73/4 R 24 Claims, 3 Drawing Figures PAIENTEB All327|914lllllill FIG. I.

APPARATUS FOR TESTING THE OPERATION 'OF THE DEFROST SWITCH IN AN AIRCONDITIONING UNIT BACKGROUND OF THE INVENTION This invention relates totesting apparatus for air conditioning systems, particularly airconditioning systems mounted on railroad cars, as described, forexample, in US. Pat. Nos. 3,486,241 and 3,694,925, assigned to theassignee of the present application, and to refrigerator cars utilizingan air conditioning system. The test system of the present invention isalso applicable to air conditioned overland trucks and generally toindustrial air conditioning systems.

In nearly all air conditioning systems some defrost must occur from timeto time. In many air conditioning systems the defrost cycle begins whenthe pressure differential across the evaporator coil reaches a desiredlevel. This pressure differential is utilized to activate a switch whichturns off a fan causing air to pass through the evaporator or may closea door preventing air to pass over the evaporator. The switch also mayactivate a heater to melt ice which may have accumulated during theprevious cooling and dehumidifying cycle.

It is very important that this switch operate properly; otherwise theair conditioning unit may freeze up, large amounts of ice may develop onthe tins of the evaporator and shut off all passageways through theevaporator. In this event, there is no air conditioning provided to thelading and lading damage is likely to result, particularly in the caseof perishable lading. The air conditioning unit also may be damaged. Innoisy installation environments it is particularly difficult todetermine if the switch is operating properly because it is oftendifficult to hear the switch click.

Therefore it is desirable that there be a reliable test to insure thatthis switch is operating properly.

It therefore is an object of the present invention to provide a testapparatus to determine if the defrost switch in an air conditioning unitis operating properly.

It is another object of the present invention to provide a testapparatus for testing the defrost air switch in which the pressure atwhich the switch operates .can be determined with close accuracy.

It is another object of the present invention to provide a testapparatus which will clearly indicate the proper operation of thedefrost switch in noisy environments.

It is another object of the present invention to provide a defrost airswitch apparatus which is inexpensive and simple to manufacture andassemble.

Other objects will be apparent from the following description anddrawings.

SUMMARY OF THE INVENTION The present invention is an improvement in airconditioning system, and comprises apparatus for testing the defrostswitch in the air conditioning system. The apparatus comprises apressure reservoir, means for filling the reservoir with fluid pressure,a pressure gauge, conduit means connecting the reservoir with thepressure gauge and with the defrost switch, and means such as a light orhorn indicating successful operation of the defrost switch. Successfuloperation of the switch is clearly indicated by the light or horn evenin noisy installation environments, and the pressure at which the switchoperates can be read on. the pressure gauge.

THE DRAWINGS FIG. I is a schematic view of an air conditioning system towhich the testing apparatus of the present invention is applicable;

FIG. 2 is a schematic illustration of the defrost air switch with theair switch testing apparatus of the present invention attached thereto;

FIG. 3 is a schematic illustration of the defrost air switch showing theposition of a movable member at the time the defrost cycle is initiated.

DETAILED DESCRIPTION The cooling and dehumidifying portion of aconventional air conditioning system is the evaporator. In FIG. 1, theevaporator 10 is provided with a coil 12 for circulating refrigerantfluid. The coil 12 may be provided with means for insuring contact withthe air for heat exchange purposes, for example, a plurality of fins 14.The evaporator is further provided with one or more air inlets l6 andair outlets 18. Air to be cooled and dehumidified passes through theinlet 16 and contacts some of the heat exchange means 14. The liquidpassing through the coil 12 cools the air and results in thecondensation of water on the fins and on the coil. During this processthe the liquid refrigerant is heated and at the end portion of theevaporator becomes a gas. One of the most common refrigerants comprisesmonofluero, trichloro methane (MFf CM). The gaseous refrigerant existsfrom the evaporator through one or more conduits 20 and passes to acompressor 22. In the compressor the gas is compressed and thetemperature of the gas is increased. From the compressor the gas passesthrough a conduit(s) 24 to a condensor 26 wherein the gas is cooled tothe liquid state usually with substantially no change in pressure. Theliquefied refrigerant then passes through a conduit(s) 27 to anexpansion valve(s) 28 wherein the temperature and pressure of the liquidare reduced. After passing through the expansion valve, the refrigerantpasses through a conduit(s) 30 into the evaporator coil 12 and the cycleis repeated. This basic air conditioning cycle is wellknown in the art.

The air conditioning system continues to function in the describedmanner until the temperature of the refrigerant sufficiently cools thefins that they reach a temperature of 30 to '3 3 F. wherein condensedwater begins to freeze on the heat exchange means (fins) and on thecoil(s). As freezing progresses and more and more ice builds up on theheat exchange means the pressure drop across the evaporator increasesbecause the ice has the effect of cutting the flow, reducing thepassages through which the air can pass. At the same time, if the systemis properly designed, the air being circulated through the system issubstantially cooled and dehumidified at this time. Most systems are setup such that when the pressure drop across the evaporator reaches acertain value a switch is activated to alter the air conditioning cycle.A conduit or tube 32 is generally provided from the exit end of theevaporator to the front end of the evaporator to a switch indicatedgenerally at 40. It will be understood that the switch could also belocated at the exit end of the unit and the conduit 32 be a bleed on theinlet air pressure. By way of example, in one air conditioning system,when the air temperature is about 55F. the pressure drop across theevaporator is approximately one inch of water. However, when thetemperature of the fins is approximately 30 to 33F, the pressure dropsoon reaches a value of around 1.25 inches of water. While these numbersvary considerably from unit to unit, this is the type of spread which isoften observed in air conditioning units and does indicate that thispressure drop is a useful means of turning off the air conditioningcycle and initiating a defrost cycle.

The switch 40 is shown in enlarged view in FIG. 2. The switch comprisesa housing 42 having an opening 44 for a pressure conduit from the inletside of the evaporator and a second conduit 46 for inlet of pressurefrom the outlet side of the evaporator. Also mounted within the housing42 is a movable member, for example a diaphragm 48. A resilient meanssuch as one or more springs 50 is affixed to the diaphragm by anyconventional means, such as a screw 52 and the other end is affixed to alever 54 by similar suitable means. Lever 54 is pivoted about a point 56and has mounted at the other end thereof a contact 58. Mounted adjacentto movable contact(s) 58 is a fixed contact(s) 60.

In the operation of the switch 40 the inlet pressure of the air goinginto the evaporator is constantly applied to the upper surface in FIG. 2of the diaphragm 48. The outlet pressure of the evaporator air isapplied to the lower surface of the diaphragm 48. The spring constant ofthe resilient means (i.e. spring 50) is biased to urge diaphragm 48upward in FIG. 2.

The inlet pressure P,- acting on the movable member (i.e. diaphragm 48)is tending to pivot lever 54 about pivot point 56. This action isresisted by spring 50 and outlet pressure P acting on the lower side ofthe diaphragm. Thus when the outlet pressure P drops to a certain level,there is no longer sufficient resistance to the application of inletpressure P,, and the lever 54 pivots about the point 56 and contact 58engages contact 60 as shown in FIG. 3. When this occurs, a relay(s) 62is activated.

Relay(s) 62 is conventional in construction including a coil 64 and amagnet 66 and a plurality of contacts 67, 68 and 69. One set ofcontacts, for example, 67 may turn off the fan 70 used to move the airthrough the evaporator or close the air inlet(s) to the evaporator.Another contact, for example, 68 may activate a heater 72 which acts tomelt the ice accumulated on heat exchange fins 14.

The defrost cycle will remain on until the thermal switch 74 (FIGS. 1and 2 comprising a thermometer or thermocouple) registers a sufficientlyhigh temperature to deactivate the contact 76. Switch 74 will theninsure that contacts 58 and 60 are parted and that lever 54 returns tothe position shown in FIG. 2. At the same time, relays 62 will activatefan 70 so that air will then again flow through the evaporator andheater 72 turned off. The air conditioning cycle will then be repeated.

The test apparatus of the present invention is indicated generally at 80and comprises a pump 82 in communication with a reservoir 84 having avalve 83 therebetween. The reservoir by means of conduit 86 is incommunication with a valve 88. By means of the valve 88, the pressurefrom reservoir 84 is applied through conduit 90 to pressure gage 92 andthrough conduit 94 to inlet 44 and diaphragm 48. Pressure gauge 92 maybe of conventional construction, for example, as described in US. Pat.No. 2,772,837. Thus, the pressure which is applied to diaphragm 48through conduit 94 may be read on gauge 92. If the switch 40 is workingproperly at the desired pressure differential, the pressure differentialbetween the two sides of the diaphragm will cause lever 54 to pviotabout point 56 and the contacts 58 and will close. As shown further inFIG. 2, a switch indicating means 96 is connected by means of lead wires97 and 98 to output contacts 61 and 63. A battery 99 or other suitablepower source may also be included in the circuit. If the pressuredifferential readable on gauge 92 causes the switch 40 to operateindicating means 96 will so indicate. For example, indicating means 96may comprise a light. If the light does not flash or if it flashes at apoint either above or below the designed pressure differential, it willbe apparent that adjustments in the switch 40 are required.Alternatively a sounding device, such as a horn, could be utilized asthe indicating means.

It will be apparent that the present testing apparatus is considerablyimproved over the prior art method of blowing into a water monometer andlistening for the switch to click. Accuracy of i0.5 inches of water isobtainable with this prior art method if the operator were able to hearthe click. Often in a field installation the power source for the airconditioning unit, such as diesel engines and/or generators, makesufficient noise that hearing the click is difficult.

With the test apparatus of the present invention improved accuracy isobtained in testing the defrost switch in the area of i 0.1 inches ofwater or a factor of roughly five.

What is claimed is:

1. Apparatus for testing a defrost switch in an air conditioninginstallation comprising:

a reservoir for containing fluid pressure; means for filling saidreservoir with fluid pressure; conduit means connecting the reservoirwith a pressure gauge and adapted to connect said reservoir with amovable member in an air conditioning system which activates a defrostswitch; and indicator means adapted to be connected to said defrostswitch indicating the operation of said switch even in noisyenvironments.

2. Apparatus according to claim 1 wherein a resilient means urges saidmovable member out of engagement with contacts in said defrost switch.

3. Apparatus according to claim 1 wherein a first conduit connects saidreservoir with said movable member and a second conduit connects saidreservoir to said pressure gauge.

4. Apparatus according to claim 3 wherein a valve is provided betweensaid reservoir and a point where said first and second conduits join.

5. Apparatus according to claim 1 wherein said means for filling saidreservoir comprises a pump.

6. Apparatus according to claim 2 wherein said movable member is aflexible diaphragm.

7. Apparatus according to claim 3 wherein the means indicatingsuccessful operation of said switch is a light.

8. Apparatus according to claim 3 wherein the means indicatingsuccessful operation of said switch is a horn.

9. in an air conditioning system in which the air conditioning unit hasa cooling and dehumidifying cycle and a defrost cycle and a switchactivates the'defrost cycle, the improvement comprising apparatus fortesting the operation of said switch including a reservoir forcontaining fluid pressure; means for filling said reservoir with fluidpressure; conduit means connecting said reservoir with a movable memberin said air conditioning system which activates said defrost switch andwith a pressure gauge; and means connected to said defrost switchindicating the operation of same.

10. In an air conditioning system according to claim 9 wherein aresilient means urges said movable member out of engagement withcontacts in said defrost switch.

11. in an air conditioning system according to claim 9 wherein a firstconduit connects said reservoir with said movable member and a secondconduit connects said reservoir to said pressure gauge.

12. ln an air conditioning system according to claim 11 wherein a valveis provided between said reservoir and a point where said first andsecond conduits join.

mounted thereon in which the air conditioning unit has a cooling anddehumidifying cycle and a defrost cycle and a switch activates thedefrost cycle, the improvement comprising apparatus for testing theoperation of said switch including a reservoir for containing fluidpressure, means for filling said reservoir with fluid pressure, conduitmeans connecting the fluid pressure with a movable member in said airconditioning system which activates said defrost switch and with apressure gauge, and means connected to said defrost switch indicatingthe operation of same.

18. In a railway car according to claim 17 wherein a resilient meansurges said movable member out of engagement with contacts in saiddefrost switch.

19. In a railway car according to claim 17 wherein a first conduitconnects said reservoir with said movable member and a second conduitconnects said reservoir to said pressure gauge.

20. In a railway car according to claim 19 wherein a valve is providedbetween said reservoir and a point where said first and second conduitsjoin.

21. In a railway car according to claim 17 wherein said means forfilling said reservoir comprises a pump.

22. In a railway car according to claim 18 wherein said movable memberis a flexible diaphragm.

23. In a railway car according to claim 19 wherein the means indicatingsuccessful operation of said switch is a light.

24. in a railway car according to claim 19 wherein the means indicatingsuccessful operation of said switch is a horn.

1. Apparatus for testing a defrost switch in an air conditioninginstallation comprising: a reservoir for containing fluid pressure;means for filling said reservoir with fluid pressure; conduit meansconnecting the reservoir with a pressure gauge and adapted to connectsaid reservoir with a movable member in an air conditioning system whichactivates a defrost switch; and indicator means adapted to be connectedto said defrost switch indicating the operation of said switch even innoisy environments.
 2. Apparatus according to claim 1 wherein aresilient means urges said movable member out of engagement withcontacts in said defrost switch.
 3. Apparatus according to claim 1wherein a first conduit connects said reservoir with said movable memberand a second conduit connects said reservoir to said pressure gauge. 4.Apparatus according to claim 3 wherein a valve is provided between saidreservoir and a point where said first and second conduits join. 5.Apparatus according to claim 1 wherein said means for filling saidreservoir comprises a pump.
 6. Apparatus according to claim 2 whereinsaid movable member is a flexible diaphragm.
 7. Apparatus according toclaim 3 wherein the means indicating successful operation of said switchis a light.
 8. Apparatus according to claim 3 wherein the meansindicating successful operation of said switch is a horn.
 9. In an airconditioning system in which the air conditioning unit has a cooling anddehumidifying cycle and a defrost cycle and a switch activates thedefrost cycle, the improvement comprising apparatus for testing theoperation of said switch including a reservoir for containing fluidpressure; means for filling said reservoir with fluid pressure; conduitmeans connecting said reservoir with a movable member in said airconditioning system which activates said defrost switch and with apressure gauge; and means connected to said defrost switch indicatingthe operation of same.
 10. In an air conditioning system according toclaim 9 wherein a resilient means urges said movable member out ofengagement with contacts in said defrost switch.
 11. In an airconditioning system according to claim 9 wherein a first conduitconnects said reservoir with said movable member and a second conduitconnects said reservoir to said pressure gauge.
 12. In an airconditioning system according to claim 11 wherein a valve is providedbetween said reservoir and a point where said first and second conduitsjoin.
 13. In an air conditioning system according to claim 9 whereinsaid means for filling said reservoir comprises a pump.
 14. In an airconditioning system according to claim 10 wherein said movable member isa flexible diaphragm.
 15. In an air conditioning system according toclaim 11 wherein the means indicating Successful operation of saidswitch is a light.
 16. In an air conditioning system according to claim11 wherein the means indicating successful operation of said switch is ahorn.
 17. In a railway car having an air conditioning system mountedthereon in which the air conditioning unit has a cooling anddehumidifying cycle and a defrost cycle and a switch activates thedefrost cycle, the improvement comprising apparatus for testing theoperation of said switch including a reservoir for containing fluidpressure, means for filling said reservoir with fluid pressure, conduitmeans connecting the fluid pressure with a movable member in said airconditioning system which activates said defrost switch and with apressure gauge, and means connected to said defrost switch indicatingthe operation of same.
 18. In a railway car according to claim 17wherein a resilient means urges said movable member out of engagementwith contacts in said defrost switch.
 19. In a railway car according toclaim 17 wherein a first conduit connects said reservoir with saidmovable member and a second conduit connects said reservoir to saidpressure gauge.
 20. In a railway car according to claim 19 wherein avalve is provided between said reservoir and a point where said firstand second conduits join.
 21. In a railway car according to claim 17wherein said means for filling said reservoir comprises a pump.
 22. In arailway car according to claim 18 wherein said movable member is aflexible diaphragm.
 23. In a railway car according to claim 19 whereinthe means indicating successful operation of said switch is a light. 24.In a railway car according to claim 19 wherein the means indicatingsuccessful operation of said switch is a horn.